4.2: Evidence

However involved the network of reasons supporting a given conclusion might be, it seems that there must be some starting points. That is, it seems there must be some reasons for believing things that don’t themselves need to be justified in terms of further reasons. Otherwise, the network of supporting reasons would go on without end. In the sciences our complex chains of reasoning seem to proceed from the evidence of the senses. We often think that sense experience provides the foundation for our edifice of scientific knowledge.

Things are actually a bit more complicated than this. We are familiar with the idea that evidence in science is based on sense experience. But there is usually a good deal going on between the raw data of sense experience and the highly processed information we count as evidence. The scientist looking at cellular structures through a microscope does have a certain visual experience. But the evidence she derives from this experience also involves her understanding of how the microscope works, how the process of slide preparation shapes her visual experience, and a good deal of background knowledge about cell anatomy. In short, our understanding of evidence is not theoretically neutral.

This holds even at the level of sense experience. In everyday life, what we experience, we experience as given. But our experience is also shaped by past experience and standing beliefs and opinions. So, while evidence may be experienced as given, it is not infallible. Our experiences can carry implicit bias, for instance. A long-forgotten dog bite in childhood may lead me to experience a barking dog as evidence of immanent threat even when there is none. Racist imagery or portrayals in media lead many of us to uncritically buy into unwarranted racist stereotypes. Given as it is, how we experience the world around us comes pre-loaded with assorted biases and judgments. Awareness of this is essential, though probably not sufficient, for remedying it. But even at the level of personal experience, what many might be tempted to call “my truth” can be quite misleading and distorted.

While sense experience can be misleading due to past experience or background beliefs and attitudes, perceiving things accurately is also much more than just “seeing clearly” in an unbiased manner. Having the right past experience and background knowledge is relevant to experiencing accurately as well. My experience of walking down a forest trail reveals no evidence of the bear that passed by a half hour ago. The evidence would have been evident to a hunter. You may pick up your phone and see a powerful micro-computer that is linked to a vast network of other computers. Your experience is simply not available to anyone who lived a century ago. What you see, hear and touch when you operate your phone is shaped by years of experience and a great deal of background knowledge and skill.

So, we are not just fallible as reasoners. People are also fallible, and improvable, right down to the level of sense experience. In addition, thinking about how to improve our understanding of evidence, and even the veracity of sense experience, leads us back to evaluating the reasons for holding our background beliefs and assumptions. Getting at understanding and knowledge is not, after all, just a matter of reasoning from a foundation based on evidence and experience. It is a matter of critically and reflectively learning from mistakes at all levels including mistaken perceptions.

Finally, we are familiar with the idea of evidence based on sense experience from science and daily life. The idea that evidence is always based on the senses mistakenly leads many people to think that philosophy is somehow evidence free. If this were true, it would probably make philosophy much easier than it is. But it isn’t true. Evidence comes in a variety of forms and not all are based on sense experience. In philosophy, for instance, philosophical problems provide a kind of evidence. When carefully reasoning from seemingly obvious assumptions leads us into contradiction or paradox, we have pretty strong evidence that at least one of our seemingly obvious assumptions is false. In everyday life, when things just don’t add up or make sense, we likewise have good evidence that we are missing something or mistaken about something.